Dynamic Host Configuration Protocol

Troubleshooting DHCP Clients

The most common DHCP client problem is a failure to obtain an IP address or other configuration parameters from the DHCP server during startup. When a client fails to obtain configuration, answer the following questions in order to quickly identify the source of the problem.

DHCP client does not have an IP address configured or has an IP address configured as 0.0.0.0.

The client was not able to contact a DHCP server and obtain an IP address lease, either because of a network hardware failure or because the DHCP server is unavailable.

Verify that the client computer has a valid, functioning network connection. First, check that related client hardware devices (cables and network adapters) are working properly at the client.

DHCP client has an auto-configured IP address that is incorrect for its current network.

The Windows 2000 or Windows 98 DHCP client could not find a DHCP server and has used the Automatic Private IP Addressing (APIPA) feature to configure its IP address. In some larger networks, disabling this feature might be desirable for network administration.

First, use the ping command to test connectivity from the client to the server. Next, verify or manually attempt to renew the client lease. Depending on your network requirements, it might be necessary to disable APIPA at the client.

Next, if the client hardware appears to be functioning properly, check that the DHCP server is available on the network by pinging it from another computer on the same network as the affected DHCP client.

Also, try releasing or renewing the client's address lease, and check the TCP/IP configuration settings on automatic addressing.

The DHCP client is missing configuration details.

The client might be missing DHCP options in its leased configuration, either because the DHCP server is not configured to distribute them or the client does not support the options distributed by the server.

For Microsoft DHCP clients, verify that the most commonly used and supported options have been configured at either the server, scope, client, or class level of option assignment. Check the DHCP option settings.

The client has the full and correct set of DHCP options assigned, but its network configuration does not appear to be working correctly. If the DHCP server is configured with an incorrect DHCP router option (option code 3) for the client's default gateway address, clients running Windows NT or Windows 2000 do not use the incorrect address. However, DHCP clients running Windows 95 use the incorrect address.

Change the IP address list for the router (default gateway) option at the applicable DHCP scope and server, and set the correct value in the Scope Options tab of the Scope Properties dialog box. In rare instances, you might have to configure the DHCP client to use a specialized list of routers different from other scope clients. In such cases, you can add a reservation and configure the router option list specifically for the reserved client.

DHCP clients are unable to get IP addresses from the server.

This problem can be caused the following:

The IP address of the DHCP server was changed and now DHCP clients cannot get IP addresses.
A DHCP server can only service requests for a scope that has a network ID that is the same as the network ID of its IP address. Make sure that the DHCP server IP address falls in the same network range as the scope it is servicing. For example, a server with an IP address in the 192.168.0.0 network cannot assign addresses from scope 10.0.0.0 unless superscopes are used.
The DHCP clients are located across a router from the subnet where the DHCP server resides and are unable to receive an address from the server.
A DHCP server can provide IP addresses to client computers on remote multiple subnets only if the router that separates them can act as a DHCP relay agent. Completing the following steps might correct this problem:
1. Configure a BOOTP/DHCP relay agent on the client subnet (that is, the same physical network segment). The relay agent can be located on the router itself or on a Windows 2000 Server computer running the DHCP Relay service component.
2. At the DHCP server, configure a scope to match the network address on the other side of the router where the affected clients are located.
3. In the scope, make sure that the subnet mask is correct for the remote subnet.
4. Use a default gateway on the network connection of the DHCP server in such a way that it is not using the same IP address as the router that supports the remote subnet where the clients are located.
5. Do not include this scope (that is, the one for the remote subnet) in superscopes configured for use on the same local subnet or segment where the DHCP server resides.
6. Make sure there is only one logical route between the DHCP server and the remote subnet clients.
Multiple DHCP servers exist on the same local area network (LAN).
Make sure that you do not configure multiple DHCP servers on the same LAN with overlapping scopes. You might want to rule out the possibility that one of the DHCP servers in question is a Small Business Server (SBS) computer. By design, the DHCP service, when running under SBS, automatically stops when it detects another DHCP server on the LAN.